From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Turmel Subject: Re: Mdadm with data offsets Date: Tue, 15 Dec 2015 08:44:36 -0500 Message-ID: <56701944.1040505@turmel.org> References: <566E0440.70801@turmel.org> <566E05B2.20803@turmel.org> <566EBC38.7060205@turmel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: "TheGerwazy ." Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 12/15/2015 06:30 AM, TheGerwazy . wrote: > The main problem is the data offsets are not stored elsewhere than in > superblock. I have some drives from debian 6.0.5 and some were changed > in debian 7.5. In 6.0.5 default data offset was at 2048 sector while > int 7.5 it is 262144. There have been other defaults, and various adjustments to the algorithms that handle special cases. The purpose of the superblock is to store the data needed by the features supported. Where else would/could you store this information? This highlights why --create is such a terrible way to recover an array, and highlights the danger posed by well-intentioned bloggers who cavalierly suggest using it. Pretty much everyone who comes here for advice *before* trying --create has been successfully helped. The results after --create are decidedly mixed. > Thanks for Phil You're welcome. Phil